Developer shut-off apparatus

ABSTRACT

A developer sump is communicated to a magnetic transport means through a developer outlet at the lower end of the sump. During development function, magnetic developer flows from the sump through the outlet to the magnetic transport means. A magnetic gate is normally located away from the outlet during the development function and is arranged to be swung into a position adjacent to the opening to magnetically stop the flow of developer through the outlet when it is desired to purge the development system.

United States Patent 1 [111 3,927,640 Smith 5] Dec. 23, 1975 DEVELOPER SHUT-OFF APPARATUS Primary Examiner-Mervin Stein 75 I z h rd Assistant Examiner-Douglas Salser 1 mentor Rm a E Smnh Webster N Y Attorney, Agent, or Firm-James J. Ralabate; Sheldon [73] Assignee: Xerox Corporation, Stamford, F. Raizes Conn.

[22] Filed: Apr. 29, 1974 [211 Appl. No.: 464,862 [57] ABSTRACT 52 us. Cl 118/637- 427/18 A developer Sump is mmunicamd 3 magneic [51] Int. Cl. G03 G 15/08 transport means through a developer mule at the [58] Field of 118/636, 637, mo. 24' and P- During development 1 7 7 222/136 1, 544. 556, 5571 magnetic developer flows from the sump through the 427/20 '8 outlet to the magnetic transport means. A magnetic gate is normally located away from the outlet during [56] Reierences Cited the development function and is arranged to be swung into a position adjacent to the opening to magnetically UNITED STATES PATENTS stop the flow of developer through the outlet when it fi'g zggis desired to purge the development system.

3,753,420 8/l973 Post et 1l8/637 OTHER PUBLICATIONS [BM Tech. Dis, 'Magnetic Brush Unit by Freeman et aI., Vol. 15, No. 4, Sept. 1972.

3 Claims, 2 Drawing Figures US. Patent Dec. 23, 1975 DEVEDOPER SHUT-OFF APPARATUS DESCRIPTION OF THE INVENTION This application is related to US. application Ser. 5 No. 464,863, filed Apr. 29, 1974, and US. application Ser. No. 464,865, filed Apr. 29, 1974, each of which are copending and commonly assigned.

It is an object of this invention to provide a magnetic brush development system with a simple and effective means for purging the system of developer material.

It is proposed to accomplish the above objective in a development system in which a developer sump has an outlet through which developer material flows therefrom to a magnetic transport system by providing a 15 magnetic gate which is located to swing into a closed position adjacent the outlet to magnetically stop the flow of the developer through the outlet to the transport system when it is desired to purge the system.

Other objects of this invention will become more apparent from the following description with reference to the drawings wherein:

FIG. 1 is a cross-sectional view of a development system illustrating a magnetic gate in open position; and

FIG. 2 is a partial view of FIG. 1 showing the magnetic gate in closed position.

Referring to FIG. 1, there is illustrated a rotatable drum having a photoconductive surface thereon and a developer housing 12 located adjacent to the drum. The photoconductive surface is adapted to receive an electrostatic latent image thereon. The developer housing includes a developer sump 13 having a quantity of developer 14 therein. The developer 14 comprises toner particles and ferromagnetic carrier particles. The triboelectric characteristics of these particles are such that the toner particles will be triboelectrically attracted to the carrier particles and the charge on the toner particles will be opposite to the charge of the latent image. A plurality o magnetic brush rollers 15 are rotatably mounted on the side walls of the developer housing 12 and are located contiguous to the photoconductive surface 10. The rollers 15 are constructed of non-magnetic material and each surround a stationary permanent magnet 16. The magnets 16 are arranged to effect a magnetic field for attracting the developer onto the rollers 15 and to present toner particles to a latent image carried by the photoconductive surface. A pair of magnetic transport" rollers 18, constructed of non-magnetic material, are rotatably mounted to the side walls of the developer housing below the magnetic brush rollers 15. A plurality of magnets 20 are located within each roller 18 and are so positioned to set up a magnetic field for attracting the magnetic developer onto the transport rollers to transport the same to the magnetic brush rollers 15.

The developer sump 13 comprises a front wall 24 separating the sump from the rollers 15 and 18, a rear sloping wall 26 and an upper wall 28 each of which are of non-magnetic material. A developer outlet 32 is located at the lowermost portion of the developer sump 13 for allowing developer to flow from the sump to the transport rollers 18. Aflixed to the upper wall 28 is a toner dispenser 34 having toner particles 36 therein which are periodically dispensed into the developer sump 13 by a rotatable foam roller 38. A pair of spaced flanges 40 (only one shown) extend from the rear wall 26 of the sump l3 and a shaft 42 is rotatably mounted thereon. A magnetic gate 44 is provided and comprises a plate 46 fixedly secured at one end to the shaft 42. A permanent magnetic bar 48 is secured to the other end of the plate and extends across the entire width of the outlet 32. A hand lever 49 is rigidly secured to the shaft 42 and may be engaged by an operators hand or be operated by a remotely controlled linkage for causing rotation of the shafi 42 and thereby the magnetic gate 44 from an open position shown in FIG. 1 to a closed position shown in FIG. 2 whereby the permanent magnet 48 engages the rear wall 26 of the sump adjacent to the outlet 32 to magnetically block the entire flow of developer through the outlet 32. Obviously, rotation of the lever in the opposite direction will reopen the magnetic gate. Detents may be employed for holding the lever 49 in a gate open or closed position.

A chute 50 is located between the upper most magnetic brush roller 15 and a residual developer opening 52 in the upper wall 28 of the developer sump 13 to direct residual developer material from the uppermost roll 15 into the sump 13. A passive cross mixer 54 is located immediately below the residual developer opening 52 and the toner dispenser 34 to receive the residual developer and fresh toner thereon and effect mixing thereof prior to discharging the same into the lower end of the developer sump 13.

In operation, an electrostatic latent image is formed on the photoconductive surface 10 in the customary manner as the drum rotates past an imaging station (not shown). The magnetic gate 44 is in the open position as shown in FIG. 1 which allows the developer to flow from the sump 13 through the outlet 32 to the magnetic transport rollers 18. The developer is carried by the magnetic transport rollers 18 to the magnetic brush rollers 15 whereby the toner particles in the developer material are presented to the latent image to develop the same as the latent image on the photoconductive surface is brought therepast. The developed image is then transferred to a copy sheet by well-known methods. Residual developer is carried to the uppermost magnetic brush roller 15 whereby upon movement of the developer out of the magnetic field of the magnet surrounded by such roller the developer is allowed to drop by gravity down the chute 50 to the residual developer opening 52 onto the cross mixer 54. Fresh toner 36 is dispensed onto the cross mixer 54 by the foam roller 38 to be mixed with the residual developer and the developer is discharged from the cross mixer to the lower end of the sump 13. This process continues through each development function.

It is customary to move the developer housing 12 away from the photoconductor drum 10 in order to repair elements on the developer housing or for replacing the photoconductor drum. Before doing this, it is most desirable to purge the system of developer to prevent developer from contaminating the rest of the machine. To do this, the lever 49 is manually engaged to rotate the shaft 42 and thereby the magnetic gate 44 into its closed position which is up against the rear wall 26 adjacent to the outlet 32 as shown in FIG. 2. The ferromagnetic developer particles are trapped within the magnetic field of the magnet 48 and thereby blocks the outlet 32 to stop further flow of the developer material from the sump to the transport rollers 18. Continued rotation of the transport rollers 18 and the magnetic brush rollers 15 delivers the developer within that portion of the developer housing to the uppermost roller 15 whereby it is discharged from the uppermost 3 roller onto the chute 50 and back into the developer sump 13 thereby purging the system of developer. After the system is purged, the developer housing 12 may be moved away from the photoconductor 10 with little chance of developer material contaminating the machine.

What is claimed is:

1. In a development system: A surface capable of having a developable image thereon, a developer housing including a developer sump, said sump having ferromagnetic developer therein, magnetic means located within said housing for presenting said developer to said surface, a developer outlet at the lowermost portion of said sump, said developer flowing through said outlet to said means for presenting said developer to said surface, and magnetic gate means located entirely exterior said housing for selectively either magnetically blocking the entire flow of developer through said outlet when in a closed position or for allowing flow of developer through said outlet when in an open position,

said magnetic gate means comprising a member having permanent magnet means secured thereto at one end and pivotally mounted to said housing at the other end for pivotal movement between said open and closed positions, and means for pivoting said member in one direction to move said permanent magnet means into said closed position adjacent said outlet to block the entire flow of developer through said outlet and for pivoting said member in the opposite direction to move said magnet away from said outlet to said open position to allow flow of developer through said outlet.

2. The structure as recited in claim 1 wherein said surface is a photoconductive surface and said developer comprises toner particles and ferromagnetic carrier particles.

3. The structure as recited in claim 2 wherein said magnetic means comprises rotatable rollers of nonmagnetic material each surrounding a magnetic member.

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1. In a development system: A surface capable of having a developable image thereon, a developer housing including a developer sump, said sump having ferromagnetic developer therein, magnetic means located within said housing for presenting said developer to said surface, a developer outlet at the lowermost portion of said sump, said developer flowing through said outlet to said means for presenting said developer to said surface, and magnetic gate means located entirely exterior said housing for selectively either magnetically blocking the entire flow of developer through said outlet when in a closed position or for allowing flow of developer through said outlet when in an open position, said magnetic gate means comprising a member having permanent magnet means secured thereto at one end and pivotally mounted to said housing at the other end for pivotal movement between said open and closed positions, and means for pivoting said member in one direction to move said permanent magnet means into said closed position adjacent said outlet to block the entire flow of developer through said outlet and for pivoting said member in the opposite direction to move said magnet away from said outlet to said open position to allow flow of developer through said outlet.
 2. The structure as recited in claim 1 wherein said surface is a photoconductive surface and said developer comprises toner particles and ferromagnetic carrier particles.
 3. The structure as recited in claim 2 wherein said magnetic means comprises rotatable rollers of non-magnetic material each surrounding a magnetic member. 